class Sass::Plugin::StalenessChecker

The class handles ‘.sss` file staleness checks via their mtime timestamps.

To speed things up two level of caches are employed:

A class-level dependency cache which stores @import paths for each file. This is a long-lived cache that is reused by every StalenessChecker instance.
Three short-lived instance-level caches, one for file mtimes, one for whether a file is stale during this particular run. and one for the parse tree for a file. These are only used by a single StalenessChecker instance.

Usage:

For a one-off staleness check of a single ‘.sss` file, the class-level {stylesheet_needs_update?} method should be used.
For a series of staleness checks (e.g. checking all files for staleness) a StalenessChecker instance should be created, and the instance-level {#stylesheet_needs_update?} method should be used. the caches should make the whole process significantly faster. WARNING: It is important not to retain the instance for too long, as its instance-level caches are never explicitly expired.

Attributes

dependencies_cache [RW]

TODO: attach this to a compiler instance. @private

dependency_cache_mutex [R]

Public Class Methods

new (options)

Source

# File lib/sass/plugin/staleness_checker.rb, line 43
def initialize(options)
  # URIs that are being actively checked for staleness. Protects against
  # import loops.
  @actively_checking = Set.new

  # Entries in the following instance-level caches are never explicitly expired.
  # Instead they are supposed to automatically go out of scope when a series of staleness
  # checks (this instance of StalenessChecker was created for) is finished.
  @mtimes, @dependencies_stale, @parse_trees = {}, {}, {}
  @options = Sass::Engine.normalize_options(options)
end

Creates a new StalenessChecker for checking the staleness of several stylesheets at once.

@param options [{Symbol => Object}]

See {file:SASS_REFERENCE.md#Options the Sass options documentation}.

stylesheet_modified_since? (template_file, mtime, importer = nil)

Source

# File lib/sass/plugin/staleness_checker.rb, line 110
def self.stylesheet_modified_since?(template_file, mtime, importer = nil)
  new(Plugin.engine_options).stylesheet_modified_since?(template_file, mtime, importer)
end

Returns whether a Sass or SCSS stylesheet has been modified since a given time.

The distinction between this method and the instance-level {#stylesheet_modified_since?} is that the instance method preserves mtime and stale-dependency caches, so it’s better to use when checking multiple stylesheets at once.

@param template_file [String] The location of the Sass or SCSS template. @param mtime [Time] The modification time to check against. @param importer [Sass::Importers::Base] The importer used to locate the stylesheet.

Defaults to the filesystem importer.

@return [Boolean] Whether the stylesheet has been modified.

stylesheet_needs_update? (css_file, template_file, importer = nil)

Source

# File lib/sass/plugin/staleness_checker.rb, line 95
def self.stylesheet_needs_update?(css_file, template_file, importer = nil)
  new(Plugin.engine_options).stylesheet_needs_update?(css_file, template_file, importer)
end

Returns whether or not a given CSS file is out of date and needs to be regenerated.

The distinction between this method and the instance-level {#stylesheet_needs_update?} is that the instance method preserves mtime and stale-dependency caches, so it’s better to use when checking multiple stylesheets at once.

@param css_file [String] The location of the CSS file to check. @param template_file [String] The location of the Sass or SCSS template

that is compiled to `css_file`.

@return [Boolean] Whether the stylesheet needs to be updated.

Public Instance Methods

stylesheet_modified_since? (template_file, mtime, importer = nil)

Source

# File lib/sass/plugin/staleness_checker.rb, line 79
def stylesheet_modified_since?(template_file, mtime, importer = nil)
  importer ||= @options[:filesystem_importer].new(".")
  dependency_updated?(mtime).call(template_file, importer)
end

Returns whether a Sass or SCSS stylesheet has been modified since a given time.

Defaults to the filesystem importer.

@return [Boolean] Whether the stylesheet has been modified.

stylesheet_needs_update? (css_file, template_file, importer = nil)

Source

# File lib/sass/plugin/staleness_checker.rb, line 62
def stylesheet_needs_update?(css_file, template_file, importer = nil)
  template_file = File.expand_path(template_file)
  begin
    css_mtime = File.mtime(css_file)
  rescue Errno::ENOENT
    return true
  end
  stylesheet_modified_since?(template_file, css_mtime, importer)
end

Returns whether or not a given CSS file is out of date and needs to be regenerated.

@param css_file [String] The location of the CSS file to check. @param template_file [String] The location of the Sass or SCSS template

that is compiled to `css_file`.

@return [Boolean] Whether the stylesheet needs to be updated.

Private Instance Methods

compute_dependencies (uri, importer)

Source

# File lib/sass/plugin/staleness_checker.rb, line 173
def compute_dependencies(uri, importer)
  tree(uri, importer).grep(Tree::ImportNode) do |n|
    next if n.css_import?
    file = n.imported_file
    key = [file.options[:filename], file.options[:importer]]
    @parse_trees[key] = file.to_tree
    key
  end.compact
end

dependencies (uri, importer)

Source

# File lib/sass/plugin/staleness_checker.rb, line 144
def dependencies(uri, importer)
  stored_mtime, dependencies =
    with_dependency_cache {|cache| Sass::Util.destructure(cache[[uri, importer]])}

  if !stored_mtime || stored_mtime < mtime(uri, importer)
    dependencies = compute_dependencies(uri, importer)
    with_dependency_cache do |cache|
      cache[[uri, importer]] = [mtime(uri, importer), dependencies]
    end
  end

  dependencies
end

dependencies_stale? (uri, importer, css_mtime)

Source

# File lib/sass/plugin/staleness_checker.rb, line 116
def dependencies_stale?(uri, importer, css_mtime)
  timestamps = @dependencies_stale[[uri, importer]] ||= {}
  timestamps.each_pair do |checked_css_mtime, is_stale|
    if checked_css_mtime <= css_mtime && !is_stale
      return false
    elsif checked_css_mtime > css_mtime && is_stale
      return true
    end
  end
  timestamps[css_mtime] = dependencies(uri, importer).any?(&dependency_updated?(css_mtime))
rescue Sass::SyntaxError
  # If there's an error finding dependencies, default to recompiling.
  true
end

dependency_updated? (css_mtime)

Source

# File lib/sass/plugin/staleness_checker.rb, line 158
def dependency_updated?(css_mtime)
  proc do |uri, importer|
    next true if @actively_checking.include?(uri)
    begin
      @actively_checking << uri
      sass_mtime = mtime(uri, importer)
      !sass_mtime ||
        sass_mtime > css_mtime ||
        dependencies_stale?(uri, importer, css_mtime)
    ensure
      @actively_checking.delete uri
    end
  end
end

mtime (uri, importer)

Source

# File lib/sass/plugin/staleness_checker.rb, line 131
def mtime(uri, importer)
  @mtimes[[uri, importer]] ||=
    begin
      mtime = importer.mtime(uri, @options)
      if mtime.nil?
        with_dependency_cache {|cache| cache.delete([uri, importer])}
        nil
      else
        mtime
      end
    end
end

tree (uri, importer)

Source

# File lib/sass/plugin/staleness_checker.rb, line 183
def tree(uri, importer)
  @parse_trees[[uri, importer]] ||= importer.find(uri, @options).to_tree
end

with_dependency_cache () { |dependencies_cache| ... }

Source

# File lib/sass/plugin/staleness_checker.rb, line 192
def with_dependency_cache
  StalenessChecker.dependency_cache_mutex.synchronize do
    yield StalenessChecker.dependencies_cache
  end
end

Get access to the global dependency cache in a threadsafe manner. Inside the block, no other thread can access the dependency cache.

@yieldparam cache [Hash] The hash that is the global dependency cache @return The value returned by the block to which this method yields